1. Technical Field of the Invention
The present invention relates generally to an improved structure of a fuel injection pump for use in internal combustion engines which results in an increase in service life of the fuel injection pump.
2. Background Art
Fuel injection pumps are known in the art which are of the type wherein a rotary mechanism such as a cam is installed eccentrically on a torque input shaft to reciprocate a plunger to pressurize fuel sucked into a compression chamber.
The torque input shaft is supported by a bearing and connected to a drive shaft of the engine through, for example, a helical gear. The use of the helical gear will cause a thrust or axial load to be produced which acts on the torque input shaft when the torque input shaft is rotated by the output of the engine, so that the rotary mechanism installed on the torque input shaft is urged in an axial direction of the torque input shaft and collides with a wall of a pump housing working as a bearing surface. The rotary mechanism, therefore, revolves in contact with the wall of the pump housing. Usually, the pump housing is made of aluminum for lightening and ease of machining. The aluminum is a relatively soft material. The revolution of the rotary mechanism in contact with the wall of the pump housing results in premature wear of the wall. This will result in an increase in undesirable oscillation of the torque input shaft and the rotary mechanism in the axial direction thereof, thus resulting in an excessive increase in wear of the pump housing, which leads to a decrease in service life of the fuel injection pump.